Talk about a "post-racial" America when President Barack Obama was elected has pretty much gone away, for good reason. Even he didn't believe it.

In fact, four years later, some disgruntled conservatives defensively accuse him of running the "most racial" presidency. That's a laughable notion, given how much this president learned the hard way (the controversies involving Harvard Professor Henry Louis Gates and slain teen Trayvon Martin come to mind) what a flashpoint public comments on race or racism can become.

Yet, so much "post-racial" happy talk was generated by the election of the nation's first president of African descent that a new divide has opened up on the question of whether his election has helped race relations or set them back.

For example, the percentage of Americans who feel race relations are getting better under Obama slid to 33 percent in an April poll by the National Journal and the University of Phoenix. Another 42 percent said they are staying about the same and 23 percent said things are getting worse.

That's a big slide from the almost-70 percent who told a poll by the Gallup organization on the day after Obama's election that they thought race relations were improving. Only 10 percent thought they were getting worse.

By October 2009, those optimistic numbers seemed to have rolled off of a cliff. After months of tea party protests and partisan bickering over Obama's health care overhaul, only 41 percent of Americans said that race relations had improved under Obama. Thirty-five percent said there was no change and 22 percent said race relations were worse.

By August of last year, Gallup found that only 35 percent saw improvement after Obama's election while 23 percent said things had gotten worse. The largest group, 41 percent, was in the "no change" column.

Tough crowd. Many are disappointed, I suspect, because they set their expectations too high. Our national divide is defined by differences in attitudes and experiences, which makes race particularly vexing. It's easy to think racism is no big deal, for example, if you haven't had to live much on the receiving end of it.

That's why the differences between black and white responses in the above-mentioned polls look almost like a slow-motion version of the racially-divided reaction to the O.J. Simpson homicide verdict: Blacks happily surprised, whites gloomily disappointed.

For the first time in the history of American polling, blacks have been expressing a rosier outlook than whites toward their long-term futures since Obama's election, despite the short-term miseries of the recession.

Unfortunately that joy sparked dread in quite a number of white Americans who didn't know what to expect from this skinny man with the funny-sounding name. Obamaphobia turned into a cottage industry on the political and social right.

This helps to explain, I believe, why recent polls show the number of Americans who think Obama is a Muslim has actually gone up. A July poll by the Pew Forum on Religion and Public Life finds 17 percent of registered voters still believe that he is a Muslim.

Not surprisingly, the poll showed the sharpest increase in self-identified Republicans, 30 percent, and "conservative Republicans," 34 percent, who say that Obama is a Muslim. That's up from 16 percent of both groups in October 2008.

By the way, Obama is a Christian, in case you missed the news.

But an expression of doubt about Obama's religion, birth certificate or -- in Donald Trump's odd case -- college grades has become a tribal identifier for many conservatives. For them it is a sign of true-blue membership in the anti-Obama flock. Just don't call it racist. That would be insensitive, even if it sounds true.

Obama "never bought into the notion" that "somehow we were entering into a post-racial period," he told Rolling Stone this year. Yet he showed in 2008 that he can find common ground with many conservatives on social issues. His sermon to a black church on the value of marriage and good parenting offended the Rev. Jesse Jackson, but reassured almost everyone else.

That's the sort of theme that he should pick up again. He might not win a lot of conservative votes, but maybe they'll treat him more like what he is, a fellow American.